Conductor paste and method of manufacturing a multilayered ceramic body using the paste

ABSTRACT

A manufacturing method for a multilayered ceramic body using Cu, Ni, Co or Fe as a conductor material, and a conductor forming paste of a particular composition of CuO, NiO, CoO or Fe 2  O 3  as the main component, the paste being applied to the multilayered body. The manufacturing method comprises: a process of forming the multilayered body with conductor paste of CuO, NiO, CoO or Fe 2  O 3  as the main component and insulating paste formed of glass and/or ceramic, so that a binder is removed from the laminate by heat treatment in an oxidizing atmosphere; a process of heat treatment for reducing the oxide; and a sintering process for sintering the laminate in a nitrogen atmosphere.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a manufacturing method for a multilayeredceramic body, such as a multilayer ceramic substrate, for mountingthereon semiconductor ICs and chips and for interconnecting them witheach other, and to a metalized composition for the multilayered ceramicbody.

2. Description of the Prior Art

The known multilayer ceramic substrate manufacturing methods areclassified into three types 1: a thick film method, 2 a green sheetprinting method and 3 a green sheet laminating method. Next, thesemethods will be described briefly. At first, the thick film method isrepresented by the hybrid IC, which employs thick film paste ofconductors and insulators and repeatedly applies to an already sinteredceramic substrate the screen process printing and baking to thereby formpatterns. This method is relatively easy to perform because the thickfilm paste is readily obtainable and the method itself is simple,thereby being now widely practiced. The thick film method, however, usesglass as the insulating layer and is not so much multilayered, therebybeing limited to three to four layers. The screen process printing andfiring are repeated for multilayering each layer to result in that along lead time and a high manufacturing cost. Also, the use of thesintered substrate will create a defect in that the through holeprocessing is difficult.

Next, the green sheet printing method uses a ceramic sheet which isfabricated by the following process. A ceramic powder (e.g. alumina orberyllia as the main component) added with an organic binder, aplasticizer and a solvent, formed in slurry by use of a ball mill, andis formed in a sheet-like film (called the green sheet) by means of thedoctor blade. The conductor paste uses high melting point metal, such astungsten (W), molybdenum (Mo) or molybdenum-manganese (Mo-Mn), and theinsulating layer paste uses paste using an inorganic component havingthe same composition as the green sheet material. In this method, theconductor paste and insulator paste are printed alternately on the greensheet to be multilayered, and after being printed and dried, thesintering is carried out at once, at which time the sintering is usuallycarried out under a reducing atmosphere in which the high melting pointmetal is not oxidized, for example, 96% alumina is sintered atemperature of 1600° C. The reducing atmosphere usually containsnitrogen and some water vapor gasses including hydrogen gas ofconcentration of about 10% (as disclosed in, for example, "A FabricationTechnique For Multilayer Ceramic Modules", Solid State Technology 15,No. 5, P 35˜40 (May, 1972)).

Such green sheet method is very advantageous and is expected to bewidely used in the future. Its advantages are as follows: Firstly, thesintering is carried out at once after the sheet is printed andmultilayered to thereby reduce manufacturing time. Secondly, theinsulating layers are the same in composition as the substrate materialand are sintered simultaneously so that a dense sintered body superiorin thermal conductivity and airtightness is obtainable. Thirdly, the useof green sheet increases the processability, such as the through holeprocessing and is superior in fine printing efficiency. Fourthly, theuse of metal, such as W, Mo or Mo-Mn, lowers material cost in comparisonwith Au or Ag/Pd series conductor material. Fifthly, the sintered bodyis shrunk when sintered, thereby being actually higher in fine lineprinting. Sixthly, adhesion strength of conductor layer is larger thanthat in the thick film method. The green sheet method, however, isdefective in that a large design change is difficult, it is dangerous tobe processed at a high temperature and to require a hydrogen atmosphere,resulting in a high fabrication cost, and the conductor is higher inelectrical resistance than Au, Ag or Cu and not to be soldered, therebyrequiring the surface treatment for plating Ni or Au on the surface.

The green sheet laminating method is similar to the green sheet printingmethod, but is different in the multilayering process of laminating anumber of green sheet printed conductors and formed through holes.

This method is effective for a large number of laminations, but requiresmolds or jigs as many as the laminations for the through hole processingto the green sheet and is low in degree of freedom for design change,thereby having been not as popular as the green sheet printing method.

Next, paying attention to the metallized conductive material used forthe ceramic substrate, the thick film method uses Au, Ag/Pd or Cu, andthe green sheet method W, Mo or Mo-Mn. The Au and Ag/Pd are fired inair, but the method is expensive due to noble metals. Also, the greensheet method, which sinters the ceramic substrate at a high temperatureof 1500° C. or more, thereby creates a problem in that the high meltingpoint metal, such as W, Mo, or Mo-Mn, only is usable. Hence, at present,a Cu metallized substrate has been noted which is low in conductorresistance, generates no migration phenomenon, and is good in soldering.Thus, the Cu metallized wiring substrate is already put into practicaluse, But, there is a drawback in the Cu metallized substrate because ofusing the base-metal. The reason for the above is that said base metal,when fired in air, is oxidized not to obtain the conductivity, and thatin order to obtain the adhesive property, sheet resistance, andsoldering property of the wiring and to eliminate decomposition oforganic binder in the paste, very delicate atmosphere control ofincluding some oxygen in the nitrogen atmosphere is required.

Furthermore, in the case where a glazed resistor and a dielectric areformed after the Cu conductor is formed, a firing atmosphere the same asthe above-mentioned one is required. However, such resistor anddielectric usable in this condition are rare and the degree of freedomfor selection is very little. Nevertheless, the merit of the base metalconductor material represented by Cu is attractive.

Now, in consideration of the future of the multilayer substrate, it willbe ideal to use the base metal material as the conductor material and toutilize the green sheet method for the multilayer method. In otherwords, a base metal conductor, such as copper, is printed on the greensheet and the insulating layer is printed or laminated in multilayers soas to obtain the multilayer substrate.

However, there are some problems to be solved in order to put the basemetal multilayer substrate into practical use. A first problem iscreated in that since the melting point of Cu, the typical base metal,is low at a temperature of 1083° C., it is necessary for sinteringsimultaneously with the substrate material to keep the sinteringtemperature thereof lower than the aforesaid melting point. This isindispensable in order to satisfy requirements as to mechanical strengthof sintered body, dielectric strength (or break-down voltage), moistureresistance and thermal conductivity of the substrate material. Furtherthe performance, such as the metallizing property of the Cu, is requiredwhen multilayered. A second problem is that it may be difficult to usethe binder under such sintering condition of temperature or atmosphere.In other words, the organic binder used for the sheet or the paste hasthe property of not decomposing in a non-oxidizing atmosphere. Unlessthe binder is completely decomposed and removed, the ceramic body itselfremains porous, whereby not only the sintering does not proceed but alsothe substrate becomes blackish due to the residual carbon is merelyobtained.

For the aforesaid simultaneously sintering substrate material,glass-ceramic material has generally been developed, which has beendisclosed in, for example, U.S. application Ser. No. 449,564(corresponding to Japanese Laid-Open Patent Application No. 50-119814)and U.S. Pat. Nos. 3,977,887 and 4,301,324, the decomposition andremoval of the binder having been disclosed in the Japanese Laid-openPatent Application No. 55-128899.

SUMMARY OF THE INVENTION

An object of the invention is to provide a method for manufacturing amultilayer ceramic body using a base metal as a conductor material.

Another object of the invention is to provide a conductor paste whichimproves the metallization performance (junction strength with thesubstrate material) of base metal (Co, Ni, Fe, or Cu) applied to theceramic laminate body.

Therefore, it is possible to obtain a high density sintered body of alow manufacturing cost, of high reliability of the metallizationperformance even in the multilayer construction.

In order to attain the above objects, a multilayered ceramic bodymanufacturing method of the invention comprises: a process of forming apattern by a conductor paste composition of base metal oxide, such asCoO, NiO, Fe₂ O₃ and CuO, as a main component, on a green sheetcomprising glass, ceramic or a mixture thereof, so that these greensheets are integrally laminated in a desired number, or a process offorming a not-sintered multilayered body by printing in thick film theconductor paste and insulator paste on the green sheet having thepattern formed and then multilayering, or a process of carrying out thethick film printing by use of the conductor paste composition of themain components of base metal oxide, such as CoO, NiO, Fe₂ O₃ or CuO,and the insulating paste composition comprising glass, ceramic or amixture thereof, on the sintered substrate of glass, ceramic or amixture thereof, thereby forming a not-sintered multilayered body; aprocess of applying to the non-sintered multilayered body a heattreatment at a temperature lower than the melting point of the glasscomposition of the insulating compositions and in an oxidizingatmosphere with respect to carbon; a process of applying to thenon-sintered body a heat treatment in an atmosphere of a mixed gas ofhydrogen and nitrogen at a temperature more than that necessary toreduce the cupric oxide to metallic copper and at a temperature lowerthan the melting point of the glass composition of the insulatingcompositions; and a process of firing the multilayered body with areducing treatment in an atmosphere of nitrogen at a temperaturenecessary to sinter the insulating compositions.

These and other objects of the invention will become more apparent inthe detailed description and examples which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an embodiment of a ceramic laminate bodyof the invention,

FIG. 2 is a sectional view of a modified embodiment of a ceramiclaminate body of the invention,

FIG. 3 is a graph exemplary of the temperature and atmosphere profile ofthe binder removing process, reduction process, and sintering process,in the manufacturing method of the invention, and

FIG. 4 is a graph exemplary of the temperature and atmosphere profile ofthe same.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a sectional view of an embodiment of a base metal multilayersubstrate manufactured by a metallizing method of the invention, inwhich reference numeral 1 designates a low temperature sinteredsubstrate composed of glass or ceramic, 2 designates a base metalmetallized layer obtained by the metallizing method of the invention,and 3 designates a through hole portion at the glass-ceramic substrate.

It is not easy to obtain a metallized multilayer substrate of basemetal, such as Co, Ni, Fe or Cu, as shown in FIG. 1. Such structure isobtained in such a manner that on the conventional green sheetcomprising a low temperature sintered insulating material and an organicbinder, such as polyvinyl butyral, the conductor paste of Co, Ni, Fe orCu is printed, so that a plurality of green sheets are laminated andbonded integrally with each other by use of heat and pressure to therebyform a multilayered body, or insulating paste having the samecomposition as the inorganic component of the green sheet and the basemetal paste are subjected repeatedly alternately to printing and dryingto thereby obtain a multilayered body, which is fired in a nitrogenatmosphere. However, it may be difficult to use the organic binder forthe firing in nitrogen, because the organic binder included in the greensheet or the insulating paste is difficult to completely remove bythermal decomposition in the non-oxidizing atmosphere and at atemperature of sintering glass-ceramic. It is well known that althoughmost of the binder is removed, a small part of the binder remains in theform of carbon. The residual carbon largely affects the sintering of theglass-ceramic material so that a dense sintered body is not obtainable.Hence, in actual firing, it is necessary for removal of the binder, toadd some oxygen from the atmosphere to thereby promote decomposition ofbinder.

While, when the oxygen (or air) to be added is too much, oxidation ofbase metal occurs, whereby the firing atmosphere requires delicatecontrol.

The present invention aims at compatibility of steps for the removal ofbinder and metallization of base metal. In other words, the method ofthe invention forms the base metal material, such as Co, Ni, Fe or Cu,into paste as oxide, which is used as the starting material for theconductor material, and utilizes the glass/ceramic low temperaturesintered material for the insulating material and forms a multilayerbody. Next, the multilayered body is subjected to a heat treatment in anoxidizing atmosphere, such as air or oxygen, thereby removing theorganic binder. It is then subjected to heat treatment for reducing thebase metal oxide, and thereafter the insulating material is applied withheat treatment for the sintering in the nitrogen atmosphere.

Next, an explanation will be given on the reason for realizing theabove. At first, regarding the binder removing process, according to themethod of the invention, since the base metal oxide to be metallized isused, under the thermal treatment even in air, the oxide causes nochange in volume, and only thermal decomposition of organic binder iscarried out, at which time the thermal decomposition should be carriedout at a temperature lower than the softening point of the glasscomposition of glass-ceramic material used as the insulating material.The reason for this is that when sintering of the laminate comprisingthe base metal oxide and insulating material proceeds in excess, thebase metal is sealed as the oxide inside the multilayered body and isnot reduced even in the subsequent reduction process and also the oxideproceeds to rapidly diffuse into the insulating layer, thereby notmaintaining the electric insulation property, at which time themetallizing material usable is limited and not effective other than Co,Ni, Fe and Cu, because oxides of these metals exist stably even at atemperature of enabling the binder to be removed. For example, the basemetal, such as W and Mo, can be present at a state of oxide WO₃ or MoO₃,but will sublimate at the temperature and in the atmosphere asabove-mentioned, thereby not being present in the laminated body, whichis not effective for the method of the invention.

Also, in a case where the volume change and unnecessary diffusion arecaused by unnecessary crystal transformation in the aforesaidtemperature region even for the oxide of Co, Ni, Fe or Cu, the body alsocannot be constructed. Therefore, it is desired in the multilayeredmethod of the invention, to employ CoO, NiO, α-Fe₂ O₃ or CuO as theoxide of Co, Ni, Fe or Cu. In other words, such oxide is stable even inair so that even when the temperature is raised in this condition, nocrystal transformation occurs and also particle sizes of the powder areselected to enable control of shrinkage rate, thereby enabling one tomake the multilayered body integrally with glass-ceramic and metal.

In addition, in the case of using an oxide, for example, Cu₂ O otherthan the above oxide, which may form CuO depending on the temperaturerise in the air, so as to cause change in volume, but is said to existas Cu₂ O in a range of 10⁻³ to 10⁻⁵ of partial pressure of oxygen,thereby enabling thermal decomposition of organic binder. The oxygenpartial pressure, however, is difficult to control as above-mentioned,which does not satisfy the purpose of the invention.

Secondly, regarding the reduction process, the base metal oxide of theinvention is reduced at a low temperature so as to be metal. Hence, itis possible to end the reduction at a temperature lower than thesoftening point of the glass-ceramic composition, resulting in the factthat the inside oxide of the not-sintered body is sufficiently reduced.At this time, the usable insulating material is limited i.e. it isrequired to be constituted of the chemically inactive component againstthe base metal conductor, because the glass-ceramic material including ametal oxide, e.g., PbO, will create a reaction given by the followingchemical formula.

    PbO+aMe→Pb+Me.sub.a O

whereby the base metal material is oxidized to form an insulatingmaterial. Furthermore, the insulator layer including Pb metal cannotdemonstrate its function as the insulator. Accordingly, when Co, Ni, Feor Cu is used as the base metal conductor, the insulating material, inorder to be stable thermodynamically and free from oxidization andreduction reactions against these elements, is required to be selectedfrom Al₂ O₃, BaO, B₂ O₃, SiO₂, CaO, MgO, Na₂ O, Ta₂ O₅, Nb₂ O₅, Li₂ Oand K₂ O.

Thirdly, regarding the firing process, the binder has already beenremoved, whereby sintering of insulating material and metallization ofbase metal need only be considered. In other words, they are heated at atemperature up to the sintering temperature of glass-ceramic and in thenitrogen gas atmosphere to so that no oxidization of the base metaloccurs, preferably, in the atmosphere of nitrogen gas of O₂concentration of 30 to 40 ppm or less. As a result of the glass-ceramicsintering and base metal particle sintering, good metallization can beobtained. At this time, however, in the case of firing the base metalnot in the neutral atmosphere, such as nitrogen, but in the reducingatmosphere, sufficient metallization is not obtainable, because theatmosphere largely affects to the wettability of the base metal to theglass-ceramic material, in other words, on the basis of the fact thatglass in the insulator layer is generally of poor wettability to metal.An oxide generally exhibits a good wettability to metal. Hence a goodwettability of oxide is realized to carry out sintering in the neutralatmosphere, making it easy to provide an extremely thin film on thesurface of the aforesaid metal.

The base metal Co, Ni, Fe or Cu used in this invention is not only usedindependently but also in desired combination so as to be effective,because the combination, as seen from the drawing, entirely forms asolid solution at all percentages, so that combinations of Cu-Ni, Cu-Co,Cu-Fe and Ni-Co do not lower the melting point below the respectivemelting point, those of Co-Fe and Ni-Fe nearly lowering the meltingpoints thereof. Hence, it is also effective to control the sinteringtemperature by combination of particles of metal and constitute alloyedwirings thereby. Also, it is effective for the multilayer wirings todesirably select the wiring conductor at each layer with Co, Ni, Fe orCu. But preferably the uppermost layer wiring should employ Ni or Cuwhich is superior in soldering efficiency.

Also, we have found that in the metallization of the invention, it isremarkably effective to add Bi₂ O₃, CdO, MnO₂ or Al₂ O₃ to each basemetal oxide of CoO, NiO, Fe₂ O₃ or CuO for improving the metallizationproperties such as adhesion strength, and it is further effective to addglass powder to the above. At this time, Bi₂ O₃, CdO and MnO₂ react withthe base metal oxide to improve bondability with the insulatingmaterial, so that Al₂ O₃ is of good wettability to the glass compositionin insulating material to be bonded thereto. The glass powder to beadded is the same as the aforesaid insulating material and should bethermodynamically stable even in the reducing atmosphere, so as not tocreate the oxidization and reduction reaction on the base metal. Forthis, it has been found that the glass powder having a compositionselected from BaO, B₂ O₃, CaO, MgO, Al₂ O₃ and SiO₂ is optimum.

In addition, the metallization method of the invention of course is notlimited to the ceramic multilayer wiring substrate, but applicable tometallization of the multilayer ceramic capacitor, or that of Fe-Niseries magnetic material to the ceramic substrate.

Next, some Examples will be detailed in the following description.

EXAMPLE 1

The ceramic substrate material used borosilicate cated glass powder(mean particle size: 3 μm) and alumina powder (Al₂ O₃, mean particlesize: 1 μm) as shown in Table 1, which are blended in a ratio of 40 to60 weight %.

                  TABLE 1                                                         ______________________________________                                        Component     Weight %                                                        ______________________________________                                        SiO.sub.2     68                                                              Al.sub.2 O.sub.3                                                                            3                                                               B.sub.2 O.sub.3                                                                             19                                                              Na.sub.2 O    0.2                                                             K.sub.2 O     8.8                                                             Li.sub.2 O    1.0                                                             ______________________________________                                    

The mixed powder was used as an inorganic component for the substratematerial, polyvinyl butyral as an organic binder, di-n-butyl phthalateas a plasticizer, and a mixture (in a ratio of 30 to 40) of toluene andisopropyl alcohol as a solvent, which were mixed in composition shown inTable 2 and slurried.

                  TABLE 2                                                         ______________________________________                                        Component          Mixing Ratio                                                                             Weight                                          ______________________________________                                        Inorganic Component                                                                              100    parts   20   kg                                     Polyvinyl Butyral  5      parts   1    kg                                     Di-n-Butyl Phthalate                                                                             5      parts   1    kg                                     Toluene/Isopropyl Alcohol                                                                        40     parts   8    kg                                     ______________________________________                                    

This slurry was sheet-molded by the doctor blade method on an organicfilm (Rumiller® 125 μm thick), at which time the system was used whichcarries out in continuation the processes of making a film, drying,punching into a desired sheet form, and through hole processing at need.The not-sintered substrate obtained as above-mentioned is called thegreen sheet. The green sheet obtained is sintered at a temperature of1000° C. in air for one hour to be a dense sintered body, whose electricperformance is such that the dielectric constant is 7.5, the dielectricloss 0.15% (1 MHz), and flexural strength is 20 kg/mm², the performancebeing of a value to nearly satisfy the requirements for a substratematerial. Next, CuO paste having main component CuO powder was used toscree-print the conductor pattern on the green sheet, the CuO powder inuse being of mean particle size of 5 μm. The vehicle composition forforming paste used a turpentine oil as the solvent and a solution ofethyl cellulose as the organic binder. These were kneaded by athree-roll blending machine with an inorganic composition of the maincomponent of the CuO powder, thereby forming paste for conductors. Onthe other hand, the insulating paste using the green sheet inorganiccomponent of the same composition as the above was formed by the methodthe same as that for the conductor paste, and after the CuO paste isscreen-process-printed, except for a portion necessary for connection,the insulating layer pattern was screen-process-printed, at which timethe printing condition for the CuO paste was to use a stainless screenof 250 meshes and of an emulsion thickness of about 20 μm, which wasabout 20 μm in thickness after being printed and dried. The insulatinglayer used a stainless screen of 200 meshes and 20 μm in emulsionthickness, which was adapted to be 45 μm in thickness by repeating twicethe printing and drying, and the green sheet was applied at both sideswith the aforesaid printing desired times. In addition, when the CuOpaste and insulating paste are produced, instead of the turpentine oiland ethyl cellulose, cellulose nitrate as the organic binder andcellulose solvents, such as butyl carbinol or butyl cellulose, may beused and also it is effective to use a surfactant, such as sorbitanalkyl ester and polyoxyethylene alkyl ether. Next, the not-sinteredlaminate obtained as above-mentioned is subject to the heat treatment bythe binder removing method of the invention. FIG. 3 shows an example ofthe binder removing system, in which the heat treatment of thetemperature profile shown in Zone 1 was carried out in air. The organicbinder in the green sheet and the organic component in the paste werealmost thermally decomposed and the organic components were removablecompletely. It is to be noted that the binder removing temperature andthe atmosphere are set by previously carrying out thermal analysis toconfirm whether or not the binder is completely removed. Accordingly,the decomposition temperature is somewhat different due to the kind ofbinder, whereby the binder removal setting temperature is of coursedifferent. At this time, when the surface of the multilayered body afterremoval of the binder is observed by a scanning electron microscope,there is found no change in particle size of the starting material forthe glass-ceramic material and also the softening of glass component isnot confirmed to result in the fact that the organic binder only hasbeen diffused. This means that the binder has been removed at atemperature lower than the softening point of glass component. Next, themultilayered body from which the binder is removed is subjected to thereduction treatment, the condition therefor being shown in Zone 2 inFIG. 3. The reduction has been carried out in the atmosphere of nitrogengas (flow rate of 2 l/min) including 10% hydrogen gas, in which thereduction temperatures of 200° C., 300° C. and 400° C. have beenmaintained for about one hour, resulting in the fact that no reductionof CuO to Cu occurs at 200° C. and reduction to Cu occurs at 300° C. and400° C. Therefore, in a case of using CuO, it is preferable to carry outreduction at a temperature of 300° to 400° C. The sintering has beencarried out under conditions depicted in the profile shown in Zone 3,resulting in the fact that a white substrate as obtained and the wiringpattern has a copper color in the interior and upper layer of thesubstrate.

Next, Tables 3 to 4 show the result of the composition, sheetresistivity, adhesive strength, and soldering wettability(solderbility), of CuO paste. In addition, the sheet resistivity wascomputed from the result of measuring by an ohmmeter a conductor patternof 250 μm in width and 25 mm in length, the soldering wettability beingqualitatively decided based on dipping the substrate in a soldering diptank. In the Tables 3 and 4, references "Excellent" and "Good" representpracticable ranges respectively. Also, the adhesive strength wasmeasured in such a manner that a lead wire of 0.8 mm in diameter issoldered (solder of Sn and Pb in a ratio of 60 to 40) vertically to apattern of 2 mm square and then a tensile tester is used to measure theadhesive strength between the substrate and the electrodes.

                                      TABLE 3                                     __________________________________________________________________________    Additive         Sintering                                                                            Sheet       Adhesive                                  Specimen Weight                                                                            CuO Temperature                                                                          Resistivity                                                                         Soldering                                                                           Strength                                  No.  Name                                                                              %   wt %                                                                              °C.                                                                           m Ω/□                                                              Wettability                                                                         kg/mm.sup.2                               __________________________________________________________________________     1   none                                                                              0   100 1000   3.91  Excellent                                                                           0.56                                       2   Bi.sub.2 O.sub.3                                                                  1   99  1000   3.82  Excellent                                                                           0.42                                       3       2   98  1000   2.78  Excellent                                                                           0.58                                       4       5   95  1000   3.18  Good  1.10                                       5       10  90  1000   3.61  Good  1.21                                       6       15  85  1000   3.85  Good  0.88                                       7       20  80  1000   5.16  Bad   0.97                                       8   CdO 1   99  1000   3.24  Excellent                                                                           0.5                                        9       2   98  1000   3.11  Excellent                                                                           0.5                                       10       5   95  1000   3.84  Good  0.71                                      11       10  90  1000   3.18  Good  0.80                                      12       15  85  1000   3.42  Good  0.69                                      13       20  80  1000   4.05  Bad   0.60                                      14   MnO.sub.2                                                                         1   99  1000   3.50  Excellent                                                                           0.62                                      15       2   98  1000   3.24  Excellent                                                                           0.65                                      16       5   95  1000   3.84  Good  1.49                                      17       10  90  1000   4.55  Good  1.50                                      18       15  85  1000   5.91  Bad   1.69                                      19       20  80  1000   8.40  Bad   0.80                                      20   Al.sub.2 O.sub.3                                                                  1   99  1000   3.30  Excellent                                                                           0.74                                      21       2   98  1000   2.61  Good  1.00                                      22   Al.sub.2 O.sub.3                                                                  5   95  1000   4.12  Good  1.18                                      23       10  90  1000   6.23  Bad   1.90                                      24       15  85  1000   10.80 Bad   1.60                                      25       20  80  1000   24.80 Bad   1.38                                      __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    Sintering Temperature 1000° C.                                                                 Sheet       Adhesive                                  Specimen                                                                           CuO Additive Amount wt %                                                                         Resistivity                                                                         Soldering                                                                           Strength                                  No.  wt %                                                                              Bi.sub.2 O.sub.3                                                                  CdO                                                                              MnO.sub.2                                                                         Al.sub.2 O.sub.3                                                                  m Ω/□                                                              Wettability                                                                         kg/mm.sup.2                               __________________________________________________________________________    26   93  2   5  --  --  3.65  Good  0.79                                      27   90  5   5  --  --  3.88  Good  1.01                                      28   85  10  5  --  --  4.28  Bad   1.42                                      29   93  2   -- 5   --  3.78  Good  1.24                                      30   90  5   -- 5   --  4.50  Good  1.83                                      31   85  10  -- 5   --  6.41  Good  2.05                                      32   93  2   -- --  5   3.64  Good  2.10                                      33   90  5   -- --  5   4.35  Good  2.23                                      34   85  10  -- --  5   8.50  Bad   1.50                                      35   93  --  2  5   --  2.65  Good  1.55                                      36   90  --  5  5   --  3.34  Good  1.86                                      37   85  --  10 5   --  3.54  Good  1.81                                      38   93  --  2  --  5   5.31  Good  1.26                                      39   90  --  5  --  5   6.25  Good  1.43                                      40   85  --  10 --  5   8.35  Bad   1.26                                      41   93  --  -- 2   5   4.32  Good  1.50                                      42   90  --  -- 5   5   6.02  Good  2.01                                      43   85  --  -- 10  5   5.99  Bad   --                                        44   94  2   2  2   --  3.24  Good  2.16                                      45   92  2   2  2   2   3.54  Good  2.33                                      46   94  '   2  2   2   4.06  Good  2.05                                      47   91  --  2  5   2   4.59  Good  2.65                                      48   86  --  2  10  2   4.83  Good  2.54                                      49   94  2   -- 2   2   3.44  Good  2.01                                      50   91  2   -- 5   2   3.79  Good  2.78                                      51   86  2   -- 10  2   4.03  Good  2.15                                      52   81  2   -- 15  2   4.51  Bad   --                                        __________________________________________________________________________

As a result, when Bi₂ O₃, CdO, MnO₂ or Al₂ O₃ is added, the adhesivestrength is seen to be effectively improved. The additive of 2 wt % ormore, when added, is effective, so that in consideration of thesoldering efficiency and sheet resistivity, the optimum amount ofadditive is about 5 to 10 wt %. From the measured results of Table 4 itis understood that each additive, even when mixed, has been improvedsimilarly in adhesive strength in comparison with CuO only.

EXAMPLE 2

When the CuO powder and each of Bi₂ O₃, CdO, MnO₂ and Al₂ O₃ shown inExample 1 were added with the glass powder, the result is shown in Table5. The glass powder is produced in such a manner that BaO, B₂ O₃, SiO₂,Al₂ O₃, CaO and MgO were mixed in the order of BaCO₃, H₃ BO₃, SiO₂, Al₂O₃, CaCO₃ and MgO and with weight % of 30, 50, 5, 10, 2.5 and 2.5respectively, the mixture was melted at a temperature of 1250° C.,dropped into water to be abruptly cooled, and after dried the glassparticles were wetground, at which time a solvent used methyl alcoholand alumina balls were used to crush the powder for 72 hours. As aresult, the glass powder of mean particle size of 2 μm was produced. Theresult is shown in Table 5.

                                      TABLE 5                                     __________________________________________________________________________    Sintering temperature 1000° C.                                         Glass     Additive     Sheet       Adhesive                                   Specimen                                                                           Amount   Amount                                                                             CuO Resistivity                                                                         Soldering                                                                           Strength                                   No.  wt % Name                                                                              wt % wt %                                                                              m Ω/□                                                              Wettability                                                                         kg/mm.sup.2                                __________________________________________________________________________     3   0    Bi.sub.2 O.sub.3                                                                  2    98  2.78  Excellent                                                                           0.58                                       53   1    "   2    97  2.50  Excellent                                                                           1.10                                       54   2    "   2    96  2.61  Excellent                                                                           1.53                                       55   5    "   2    93  2.96  Good  2.20                                       56   10   "   2    88  3.12  Bad   2.32                                       57   15   "   2    83  4.55  Bad   --                                         58   1    "   5    94  3.54  Excellent                                                                           1.55                                       59   2    "   5    93  3.02  Good  1.83                                       60   5    "   5    90  3.10  Good  2.40                                       61   10   "   5    85  3.33  Bad   2.00                                       62   15   "   5    80  4.54  Bad   --                                         63   1    CdO 2    97  2.78  Excellent                                                                           0.73                                       64   2    "   2    96  3.18  Good  0.65                                       65   5    "   2    93  3.61  Good  1.10                                       66   10   "   2    88  3.82  Bad   1.35                                       67   15   "   2    83  6.15  Bad   --                                         68   1    MnO.sub.2                                                                         2    97  3.35  Excellent                                                                           0.98                                       69   2    "   2    96  3.34  Excellent                                                                           1.78                                       70   5    "   2    93  4.18  Good  2.78                                       71   10   "   2    88  5.79  Bad   2.65                                       72   15   "   2    83  9.10  Bad   --                                         73   1    Al.sub.2 O.sub.3                                                                  2    97  2.73  Excellent                                                                           1.55                                       74   2    "   2    96  2.61  Good  1.96                                       75   5    "   2    93  4.12  Good  2.73                                       76   10   "   2    88  6.23  Bad   2.55                                       77   15   "   2    83  10.8  Bad   --                                         __________________________________________________________________________

As a result, it is seen that the glass powder is added to effectivelyimprove the adhesive strength. In addition, the addition of glass powderof 1 wt % or more is effective, while, addition of the same of 10 wt %or more deteriorates the solder wettability. Hence, it is consideredthat an optimum amount is about 2 to 5 wt %. Alternatively, thecomponent other than BaO, B₂ O₃, CaO, MgO, Al₂ O₃ and SiO₂ in thisembodiment of course is acceptable unless the sintering in the reducingatmosphere will oxidize CuO.

EXAMPLE 3

In this example, the ceramic substrate already sintered was used as thebase. In other words, the alumina powder is the main component and isadded with SiO, MgO or CaO powder as a sintering assistant, so thatalumina as a whole is 96% by weight percent (called the 96% alumina) andthe substrate is sintered at a temperature of 1600° C., which is of50×50 in width and 0.8 mm in thickness. Then, the conductor paste of themain component CoO, Fe₂ O₃ and NiO, and borosilicate glass (shown inTable 1) the same as Example 1 are mixed at a mixing ratio of 30 to 70wt % with respect to alumina to be mixed, so that the mixture is used asthe insulating paste and is repeatedly printed the desired times on thealumina substrate and multilayered. FIG. 2 shows this construction insection, in which reference numeral 1 designates a glass-ceramic layerin this embodiment, 2 designates a base metal metallized layer, and 4designates a sintered 96% alumina substrate. The heat treatment forbinder removal, reduction and firing, was as aforesaid carried out bythe temperature profile shown in FIG. 4. The example 3 is different fromthe examples 1 and 2 in that the reducing temperature is raised to atemperature (about 500° C.) to enable reduction of CoO, NiO and Fe₂ O₃,and the baking temperature is raised to 1000° to 1400° C. because Co,Ni, and Fe of high melting point in comparison with Cu are used. Theevaluation of the performance of the multilayer substrate obtained asabove-mentioned are shown in Tables 6 to 8. In addition, since Fe and Cocannot be soldered, the wiring pattern of the main component of Co or Fehas been applied with electroless Cu plating, and subjected to heattreatment at a temperature of 500° C. and in vacuum, so that theadhesive property between Co or Fe and the Cu plated layer has beenimproved and then the adhesive strength of insulating layer andelectrode has been measured.

                  TABLE 6                                                         ______________________________________                                                                       Sintering                                      Speci- Additive                Tempera-                                                                             Adhesive                                men             Amount    CoO    ture   Strength                              No.    Name     wt %      wt %   °C.                                                                           kg/mm.sup.2                           ______________________________________                                        78     none     0         100    1200   0.30                                  79     Bi.sub.2 O.sub.3                                                                       1         99     1200   0.35                                  80              2         98     1200   0.88                                  81              5         95     1200   0.95                                  82              10        90     1200   0.78                                  83              15        85     1200   0.55                                  84              20        80     1200   0.78                                  85     CdO      1         99     1200   0.15                                  86              2         98     1200   0.63                                  87              5         95     1200   0.45                                  88              10        90     1200   0.58                                  89              15        85     1200   0.78                                  90              20        80     1200   0.25                                  91     MnO.sub.2                                                                              1         99     1200   0.33                                  92              2         98     1200   0.58                                  93              5         95     1200   0.78                                  94              10        90     1200   1.03                                  95              15        85     1200   0.59                                  96              20        80     1200   0.35                                  97     Al.sub.2 O.sub.3                                                                       1         99     1200   0.33                                  98              2         98     1200   0.47                                  99              5         95     1200   0.78                                  100             10        90     1200   0.95                                  101             15        85     1200   0.38                                  102             20        80     1200   0.65                                  103    CuO      1         99     1200   0.25                                  104             2         98     1200   0.38                                  105             5         95     1200   0.79                                  106             10        90     1200   1.05                                  107             15        85     1200   1.22                                  108             20        80     1200   0.63                                  ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                                                       Sintering                                      Speci- Additive                Tempera-                                                                             Adhesive                                men             Amount    Fe.sub.2 O.sub.3                                                                     ture   Strength                              No.    Name     wt %      wt %   °C.                                                                           kg/mm.sup.2                           ______________________________________                                        109    none     0         100    1400   0.33                                  110    Bi.sub.2 O.sub.3                                                                       1         99     1400   0.44                                  111             2         98     1400   0.39                                  112             5         95     1400   0.78                                  113             10        90     1400   0.81                                  114             15        85     1400   0.70                                  115             20        80     1400   0.55                                  116    CdO      1         99     1400   0.51                                  117             2         98     1400   0.75                                  118             5         95     1400   0.98                                  119             10        90     1400   1.11                                  120             15        85     1400   0.55                                  121             20        80     1400   0.78                                  122    MnO.sub.2                                                                              1         99     1400   0.41                                  123             2         98     1400   0.75                                  124             5         95     1400   0.88                                  125             10        90     1400   0.66                                  126             15        85     1400   0.54                                  127             20        80     1400   0.49                                  128    Al.sub.2 O.sub.3                                                                       1         99     1400   0.51                                  129             2         98     1400   0.99                                  130             5         95     1400   0.85                                  131             10        90     1400   1.41                                  132             15        85     1400   1.20                                  133             20        80     1400   1.01                                  134    CuO      1         99     1400   0.59                                  135             2         98     1400   0.89                                  136             5         95     1400   1.25                                  137             10        90     1400   1.17                                  138             15        85     1400   1.10                                  139             20        80     1400   1.06                                  ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                                                  Sintering                                                                            Solder-                                      Speci-                                                                              Additive            Tempera-                                                                             ing    Adhesive                              men           Amount        ture   Wet-   Strength                            No.   Name    wt %     NiO  °C.                                                                           tability                                                                             kg/mm.sup.2                         ______________________________________                                        140   0       0        100  1000   Excellent                                                                            0.54                                141   Bi.sub.2 O.sub.3                                                                      1        99   1000   Excellent                                                                            1.20                                142           2        98          Excellent                                                                            1.88                                143           5        95          Good   2.78                                144           10       90          Good   2.87                                145           15       85          Bad    2.83                                146           20       80          Bad    2.79                                147   CdO     1        99   1000   Excellent                                                                            0.88                                148           2        98          Excellent                                                                            0.95                                149           5        95          Excellent                                                                            1.35                                150           10       90          Good   1.83                                151           15       85          Bad    1.55                                152           20       80          Bad    1.95                                153   MnO.sub.2                                                                             1        99   1000   Excellent                                                                            1.20                                154           2        98          Excellent                                                                            1.65                                155           5        95          Excellent                                                                            1.38                                156           10       90          Good   1.78                                157           15       85          Bad    1.65                                158           20       80          Bad    1.53                                159   Al.sub.2 O.sub.3                                                                      1        99   1000   Excellent                                                                            1.10                                160           2        98          Excellent                                                                            1.54                                161           5        95          Good   1.98                                162           10       90          Good   2.78                                163           15       85          Bad    2.54                                164           20       80          Bad    1.89                                165   CuO     1        99   1000   Excellent                                                                            1.43                                166           2        98          Excellent                                                                            2.75                                167           5        95          Excellent                                                                            3.01                                168           10       90          Good   3.25                                169           15       85          Good   2.98                                170           20       80          Good   2.54                                ______________________________________                                    

As seen from this example, even when CoO, NiO and Fe₂ O₃ were used, aresult the same as when using CuO was obtained, which clarified thatmetallization of base metal of a low cost was performed easily on themultilayered ceramic substrate. In addition, in Tables 6 to 8, Bi₂ O₃,CdO, MnO₂, Al₂ O₃ or CuO were used independently as the additive, butthe combination thereof exhibited a similar tendency.

EXAMPLE 4

In the series of CoO, NiO and Fe₂ O₃ added with Bi₂ O₃, CdO, MnO₂, Al₂O₃ and CuO as the additive, the effect of adding to them the glasspowder in Example 2 was examined, which is shown in Tables 9 to 11.

                  TABLE 9                                                         ______________________________________                                                                        Sintering                                     Speci- Amount                   Tempera-                                                                             Adhesive                               men    of Glass Bi.sub.2 O.sub.3                                                                       Fe.sub.2 O.sub.3                                                                     ture   Strength                               No.    wt %     wt %     wt %   °C.                                                                           kg/mm.sup.2                            ______________________________________                                        171    0        2        98     1400   0.39                                   172    1        2        97     1400   1.15                                   173    2        2        96     1400   1.53                                   174    5        2        93     1400   1.88                                   175    10       2        88     1400   2.12                                   176    15       2        83     1400   1.66                                   177    20       2        78     1400   1.30                                   178    1        5        94     1400   1.01                                   179    2        5        93     1400   1.73                                   180    5        5        90     1400   2.10                                   181    10       5        85     1400   2.00                                   182    15       5        80     1400   1.53                                   183    20       5        75     1400   1.58                                   ______________________________________                                    

                  TABLE 10                                                        ______________________________________                                                                        Sintering                                     Speci- Amount                   Tempera-                                                                             Adhesive                               men    of Glass Bi.sub.2 O.sub.3                                                                       CoO    ture   Strength                               No.    wt %     wt %     wt %   °C.                                                                           kg/mm.sup.2                            ______________________________________                                        184    0        2        98     1200   0.88                                   185    1        2        97     1200   0.75                                   186    2        2        96     1200   1.23                                   187    5        2        93     1200   1.55                                   188    10       2        88     1200   1.45                                   189    15       2        83     1200   1.62                                   190    20       2        78     1200   1.33                                   191    1        5        94     1200   0.93                                   192    2        5        93     1200   1.25                                   193    5        5        90     1200   1.46                                   194    10       5        85     1200   1.88                                   195    15       5        80     1200   1.38                                   196    20       5        75     1200   1.01                                   ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                                                     Sintering                                                                            Solder-                                   Speci-                                                                              Amount                 Tempera-                                                                             ing   Adhesive                            men   of Glass Bi.sub.2 O.sub.3                                                                      NiO   ture   Wetta-                                                                              Strength                            No.   wt %     wt %    wt %  °C.                                                                           bility                                                                              kg/mm.sup.2                         ______________________________________                                        197   0        2       98    1000   Excel-                                                                              1.88                                                                    lent                                      198   1        2       97    1000   Good  2.78                                199   2        2       96    1000   Good  3.12                                200   5        2       93    1000   Bad   3.34                                201   10       2       88    1000   Bad   --                                  202   15       2       83    1000   Bad   --                                  203   1        5       94    1000   Excel-                                                                              2.12                                                                    lent                                      204   2        5       93    1000   Excel-                                                                              2.72                                                                    lent                                      205   5        5       90    1000   Bad   3.35                                206   10       5       85    1000   Bad   3.93                                207   15       5       80    1000   Bad   --                                  ______________________________________                                    

As seen from Tables 8 to 11, the addition of glass powder as the same asCuO is expected to improve the adhesive strength. Alternatively, themetal oxide other than Bi₂ O₃ in this example may be used to obtain thesame effect, or glass only, even when added to the base metal, is alsoeffective.

Although several examples have been described, they are merely exemplaryof the invention and are not to be construed as limiting, the inventionbeing defined solely by the appended claims.

What is claimed is:
 1. A conductor paste comprising: an inorganiccomponent comprising CuO powder at 85 to 98 wt % and at least one of Bi₂O₃, CdO, MnO₂ and Al₂ O₃ at 2 to 15 wt %; an organic binder; and asolvent for the binder.
 2. A conductor paste comprising: an inorganiccomponent comprising CuO powder at 75 to 97 wt %, glass powder at 1 to10 wt %, and at least one of Bi₂ O₃, CdO, MnO₂ and Al₂ O₃ at 2 to 15 wt%; an organic binder and a solvent for the binder.
 3. The conductorpaste as set forth in claim 2, wherein said glass powder comprises anoxide selected from the group consisting of BaO, B₂ O₃, CaO, MgO, Al₂ O₃and SiO₂.
 4. A conductor paste comprising: an inorganic componentcomprising a powder of one of NiO, Fe₂ O₃ and CoO, at 85 to 98 wt % andat least one of Bi₂ O₃, CdO, MnO₂, Al₂ O₃, and CuO, at 2 to 15 wt%; anorganic binder; and a solvent for the binder.
 5. A conductor pastecomprising: an inorganic component comprising a powder of one of NiO,Fe₂ O₃ and CoO, at 75 to 97 wt %, glass powder at 1 to 10 wt %, and atleast one of Bi₂ O₃, CdO, MnO₂, Al₂ O₃, and CuO, at 2 to 15 wt %; anorganic binder, and a solvent for the binder.
 6. The conductor paste asset forth in claim 5, wherein said glass powder comprises, as acomponent, an oxide selected from BaO, B₂ O₃, CaO, MgO, Al₂ O₃ and SiO₂.